Index: sys/conf/kern.pre.mk
===================================================================
--- sys/conf/kern.pre.mk
+++ sys/conf/kern.pre.mk
@@ -93,7 +93,11 @@
 .if defined(CFLAGS_ARCH_PARAMS)
 CFLAGS.gcc+=${CFLAGS_ARCH_PARAMS}
 .endif
+.if ${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} < 50000)
+WERROR?= -Wno-error
+.else
 WERROR?= -Werror
+.endif
 
 # XXX LOCORE means "don't declare C stuff" not "for locore.s".
 ASM_CFLAGS= -x assembler-with-cpp -DLOCORE ${CFLAGS} ${ASM_CFLAGS.${.IMPSRC:T}} 
Index: sys/conf/kmod.mk
===================================================================
--- sys/conf/kmod.mk
+++ sys/conf/kmod.mk
@@ -107,7 +107,12 @@
 .if !empty(CFLAGS:M-O[23s]) && empty(CFLAGS:M-fno-strict-aliasing)
 CFLAGS+=	-fno-strict-aliasing
 .endif
-WERROR?=	-Werror
+.if ${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} < 50000)
+WERROR?= -Wno-error
+.else
+WERROR?= -Werror
+.endif
+
 CFLAGS+=	${WERROR}
 CFLAGS+=	-D_KERNEL
 CFLAGS+=	-DKLD_MODULE